cunningham



Jan. 6,- 1942.

L: L: CUNNINGHAM BURNER CONTROL SYSTEM A. :origimaa Filed July 19, 1959 js 'smeg-:snee: 1

llrllllllllllllll l INVENTQR Lamas LEunmz-zgham Jan. 6, 1942. CLJNMNGl--IAM Re. 21,993

BURNR' CONTROL SYSTEM' Original Fil'ed July 19, 1939 5 Shets-Sheet 2' ATTORNEY.

L. L."CUNNINGHAM BURNER CONTROL SYSTEM original 'Filed July 19, 1939 3 Sheets-Sheet 5 v mvxfrN-rom` ham Lewis f eissued Jan. 6, 1942 nomina comer. srsrEM Lewis L. Cunningham, Glendale Calif., assignor to Perlen Corporation Milwaukee, Wis., a corporation oi Wisconsin origami No. amarte, esta: april as", mo, serai nu. essere, .my in, iosa .Application :er i-e- 'l'hls invention relates in general to control sys` tems and more particularly to oil burner control systems.

In oil burner control systems it is customary toprovide some means whichwill, in case of ignition failureor flame failure, s hut'the oil burner down until such means has been manually reset. Such means is generally referred to as a safety switch or lockout switch and usually consists of a switch, a pair of bimetal actuators, and one or two electric heaters. If one of the heaters remains energized for too long a period 'cr if a second heater is not energized after a predetermined time period, the safety switch opens and thereafter remains open until manually reset. The safety switch is usually responsive to combustion conditions. Generally, electric ignition is used for oil burners and if theV ignition is letton during the entire period of operation, it is` referred to as constant-ignition, whereas if the ignition ignition. A

In intermittent ignition systemalt is custom- Vary to turnthe ignition oii' by a switch which isV responsiveto combustion conditions, such as a switch operated by a piece of bimetal' which projects into the furnace stack.. customarily there are or may be various additional auxiliary controls which 'cooperate to give an entirely autoor may not be incorporated ,with the present invention vand whose use will not be discussed here. The primary object of this invention is to protrolling. the operation of automatic fuel burners,

mittent ignition type,

ignition period ior` intermittent ignitionV oil burners.

a new and improved timing arrangement for the Another 'object of ignitionperiod for intermittent ignition oil burn# ers. vwhich ,will insure giving an ignition period which will never fall below a certain selected l .minimum length of time.

Another object of this invention is to provide 56 the second form of the invention.

and more particularly oil burners of the inter` Another object of this invention is to provide' anew and improved timing arrangement for the ignition period for intermittent ignition oil burners which is not responsive to combustion con-` lditlons alone.

is discontinued a' short time after combustion has been established, it is referred to as intermittent.

matic system. These controls may be high or low limit controls, low water cut offs, etc.. which mayv ..35 vide new and improved control systems for ccn- Another object oi this invention is-to provide i this invention is to provide a new and improved timing arrangement for the n by or idle position.

issue March 1li, 1941, Serial No. 383,957

3 (Ilalms. (Cl. 158-28) Another object of the invention is to provide a simplified oil burner control system which will automatically recycle after a power failure immediately upon the resumption of power. but which will not recycle aitera ame or ignition failure.

Other objects and advantages reside in certain novel featuresA ci the construction, circuit arrangement and operation of thevarlous parts and arrangementswhich will be hereinafter more fully described in the speciilcaton and particularly pointed out in the `appended claims, and of which a preferred embodiment is illustrated in the accompanying sheets of drawings forming a part thereof. In the drawings:l

Fig. 1 shows a iront elevation of the invention.

Fig. 2 shows a side elevation of the invention y depicting in detail the construction oi the combustion responsive mechanism.

Fig. 3 is a perspective view showing the details of the combustion responsive switches of theinvention.

Fig. 4 illustrates the details of the ignition timing mechanism as seen from the section line 4-4 of Fig. l.

Fig. s shows the detain or the isniuonnming mechanism as seen from the section Aline 5-5 of Fig. l.

Fig. 6 is an end view of the ignition timing mechanism showing the mechanismin the stand--l Fig. 'Iris an end view of the ignition` timing mechanism showing the mechanism during the' ignition period of the operating or running period.

Fig. 8 is also an end view of the ignition timing mechanism, but shows the mechanism during the operating or running period after the ignition period has expired; f

Fig. 9 is an exploded perspective viewshowing the details of the ignition timing mechanism.

Fig. 10 is a semi-schematic wiring diagram of one form of the invention.

Fig. 11 is a full schematic/wiring diagram oi one form oi' the invention.

l2 is a semi-schematic wiring diagram of' the second form of the invention.

Fig. 13 is a full schematic'wiring diagram of are supported by the panel I8 and are adapted to receive electrical conductors (not shown).

i Terminals I8 and I8 receive conductorsfrom a source of power. Terminals I8 'and 2i receive conductors from a fuel feeding means. -Terxninais I8 and 22 receive conductors from an`igniting means, and terminals 23 and 24 receive conductors from an automatic operating device such as a thermostat. A pair of mutually coupled reactance coils here shown as a choke or transformer' 25 are supported on the base I5. A means for controlling the fuel feeding means and the ignition means such as an electromagnetic relay 28 is additionally supported on the hase I5. An armature 21 for the relay is pivoted at the point 28. An interlocking arm 28 is fastened to the relay amature 21 by means of screws 3l. An interlocking armature 321s secured to the interlocking arm 28 by means of an insulating member 33, rivets 34, screws 35 and two-hole bracket 35. The armature 32 is threaded and slotted to receive and frictionally secure'a pull-in voltage adjusting screw 31 adapted to engage the panel I8 and thereby limit the motion ofthe armature 32 in one direction.

A movable contact assembly 38 is insulatively secured to the relay armature 21. Stationary contacts 38, 4I and 42 mounted on the panel I8 cooperate with the 'movable contact assembly 38 to perform certain switching functions whichvwill be more fully explained hereinafter.

A .thermal dement bracket ur1g..2 is sadil' tionally fastened to the base I5 by means of screws 44. A combustion responsive means such as a U-shaped channel expansible element and' v a cooperating relatively inexpansible tubular element 48 are provided. The expansible element 45 is secured to the thermal element bracket '43 by means of rivets 41. The tubular element 48.

is 4secured at one of its ends to the middle of the expansible U-shaped element 45 by a rivet 48 and the other of its ends is adapted to pass through an aperture in the'thermal element bracket 43 and the base' I5 and to receive a flexible slip frictionelement 48. A U-shap'ed slip friction housing element or actuator 5I is pivotally secludes an active bimetal blade 51 and a compensating bimetal blade 58 arranged to compensate the activeblade 51 for changes in ambient temperature. A motivating heater 58 for the active blade 51 is surrounded and secured by a heat absorbing mass 8| which is in turn fastened to the `active blade 51. A motivating heater 82 for the compensating blade 58 is secured thereto by an adjustable heat absorbing clamp 83. A latch 84 is arranged to cooperate with the active and compensative bimetal blades 51 and 58 in order to open a pair of switch contacts 85 in the event the active blade 51 deflects in excess of a certain set amount relative to the compensating blade 58. A reset lever 88 together with its reset switch 81 cooperates with the latch 84 to enable the latch to be reset by a manual operation.y For a general disclosure of the lockout switch herein described reference may be had to copending applications of Herbert E. Lindemann, filed May 31, 1938. Serial No. 210,867 and'J. A. Deubel, flied October 24, 1938, Serial No. 236,819.

Means are also mounted on the base I8 for deenergiz'ing the igniting means after an ignition period. Referring Particularly to Figs., 1 and also 4, 5, 6, 7 and 8, an active bimetal element 88 is secured at a spaced distance to a movable U- shaped support bracket 88 by means of rivets 1I, spacers 12, and a projecting portion of a motivating heater' bracket 13. A motivating heater 14 is secured by the motivating 'heater bracket V13 in a manner suitable to allow the heat generated by the heater 14 to affect the active bimetal element 88.- A switch armature 15 is fastened to the free end of the active bimetal blade 88 by rivets 18 to assume a position substantially opposite the interlocking armature 32. One end of a compen- .sativebimetal element 11 is additionally secured 'at aspaced distance tothe U-shaped supporting 40' bracket 88 by rivets 18 and spacers 18 and is disposed to extend side by side'and parallel to the activebimetal element 88. A stationary U- y shaped bracket 8| is fastened to the panel I8 by Vmeans of rivets 82 and is adapted to cooperate with the movable U-shaped support Vbracket 88 and a hinge pin 83 to form a pin hinge. An ad.-

`justing lug 84, which is threaded and slotted to l receive and frictlonally secure a support such as an adjusting screw 35,. is fastened to the free end of the'compensating element 11 by means of y rivets. 88.

cured by a spring hinge 52 toa projecting lug 58 on the thermal element bracket 43: A spring loaded pressure pad 54 isarranged to apply pressure to the flexible4 slip friction element 48 through two blocksof friction material 55. This arrangement permits linear motion of the inlexpansible tube 48 to be converted to rotary motion of the slip friction housing element 5I'1an'd further permits unlimited motion or the mex; pansible tube 48- although the slip friction house ing element 5I is-restrained from moving.A A screw and spring 58 provide means for adjusting the. pressure applied tothe lflexible slip friction element 48. -For a more detailed disclosure of the combustion responsiveA element and the slip friction means reference may be'had to a copending application of William Christiansen. Serial No. 236,818, flied October- 24, 1938.

A lockout or safety switch for rendering thel fuel feeding and the ignition means inoperative The adjusting screw 85 provides 'an adjustment for the'` elevation of the compensating bimetal element 11 abovev the panel I8 and this in turn adjusts the length of the ignition period as'will be more fully disclosed hereinafter.

Magnetic biasing means for the ignition switch such as a horse shoe magnet 81 is secured to a right angle support 88 bymeans of a screw 88 passing throughtheopening between the poles of the lmagnet and threading into a plate 8 I. One leg of the right angle support 88 projects through an-aperture 82 in the panel I8', while the other leg is disposed torest upon and is secured to the panel I8 .by screws 83 passing through the panel I'8 from the under side and threading -into the right angle support 88. With the right angle -support. 88 mounted in this manner the permanent magnet 81 also projects through the aperture 82fin lthe panel I8 and its poles are positioned directly below the interlocking armature Y 82 and the switch armature 15 in order that the two armatures win be mutually attracted to it.'

The right angle bracket 88 is slotted and threaded is also supported on the panel I8. -This switch into receiveV and frictionallyv secure acontact screw `ture is in its innermost position.

94. A spring contact blade 95 carrying a contact 96 is secured to the panel 'I8 by screws 91 threading into a keeper 98. The spring blade 85 is positioned so that the contact 88 engages the contact screw 94 as well` as contact 98 carried on the switch armature 15 when the switch arma- (See Fig'. 5.) A latch such as the spring latch |09 having a catch and a release slide IBI-A, also'projects through the aperture 92 and is arranged-to cooperate with the switch amature and the interlocking armature 32 to perform certain functions as will be more fully pointed out hereinafter. The spring latch |08 is fastened to one leg of a latch bracket |02 by rivets |83 while the other leg is secured to the back of the panel It by rivets |04. (SeeFig. 6.)' An S-shaped bracket |05 for limiting the outward motion of the active bimetal element 88 is fastened to the front of the panel I6 by the rivets |04, which also secure latch bracket |02.

Two pairs of combustion responsive contacts |06 and |01 (see Figs. 2 and 3) for controlling the lockout switch and the starting circuit respectively, are supportedI on the panel I8 and arel disu posed directly behind an insulating member |08 which is securedvtc the slip yfriction housing or actuator 5I` by screws |09. Switch operating screws |I| and ||2 projectthrough the insulat-V ing member |08 and serve to operate switches |08 and |01,A respectively, in response-to the action of the slip friction housing or actuator 5I.

A projection H3 on the relay insulating member 33 (Figs. 2 and 3) 4is disposed to open the contacts -|||8 when the relay is in the open position regardless of the position of the lslip friction insulating member |08. v

The combustion responsive switch |01 is merely an accessory switchffor interposing delay between successive motor energizations. It is not entirely kessential to the satisfactory operation of the system and may be shunted out of the circuit `if the delay it produces is not desirable under some conditions of operation. f

-Afv "cold stop pinv |I4"is fastened to a stop bracket H5 whichin turn is secured to-the panel I8 and the base` I5 by suitable means. .A movable "hotf stop I|8 projects through'a' slot ||1 in the stop bracket' H5 and is. fastened to an adjustlns arm V| I8 which is pivoted by a screw ||9. The col stop ||4 andthe hot stop ||6 serveto limit the motion of the to the stop bracket ||5 ductors |23 and |24. Relay contacts 38 serve as holding contacts and connect from one side of the ignition switch 99 to one side of the line through conductor |23. An igniting means |28 is connected in series with the relay contacts 4|. One side of this series combination is connected to one-side of the line by the conductor |24 and the other side is .connected to the junction between the ignition switches 94 and 99. The ignition switch motivating heater 14 in series with a voltage dropping resistor |29 is connected in parallel with the igniting means |28.

Operation Under lnormal standby conditions a small current flows through the relay circuit extending from conductor |23 through the normally closed combustion responsive contacts |01, through the normally closed ignition switch contacts 94 and 99, through the normally closed safety switch contacts 65, and reset contacts 61, through the transformer primary 25, through the relay 28, to the conductor |24. Relay contacts 38, 39 and 4|, combustion responsive contacts |06, and thermostat contacts |25 are all open under these conditions.

Normal start I! the temperature in the space being heate falls below a predetermined point,` the thermostat contacts |25 close and the lockout resistor 58 is shunted across thesecondary of the' transformer 25. Closing the transformer secondary circuit causes a considerably greater amount of current to flow in the, relay circuit. The relay 26 is then sufliciently energized to attract its armature.

Theccntacts 38, 39 and 4| close and the interlocking armature 32 lifts out of release slide IGI-A and allows the catch |0l' to spring once and rest against the edge of the switch armature 15.

slip friction insulating member `HI8 as will be morevfully explained hereinafter.

Rotating the adJusting arm'lI 8 moves the hot"' .f

stop |`|v relative to thecold' stop |4 and serves to change the' amount vof travel of the insulating member |08.

The adjustablehot stop H8 shown herein is an accessory not essentialto the satisfactory performance of the Jsystem. It may be replaced by.A

a fixed stop if "such is found to be desirable.

Referring nowparticularly to Figs. 10 and l1 IVI showing circuitdiagramsof one formof the system:

Conductors |2| and |22 leading fromthe source Yof power are connected to' the terminals |8 and ll.

A circuit path extends from terminal I8, through l a conductor |23, through the combustion responsive contacts |01..,through .the ignition contacts 94 and 99, through .the lockout switch contacts 85,through theresetcontacts 81, through V'the high voltage or primary side of the transformer 25,' through the relaycoil Il ,through a conductor |24 to the other side of the line at terminal I8.

r vand causes counterclockwise deilectionof the slip manent magnet 81.

(See Fig. '1.) As a result the motor |25 isenergized from the line through conductors |23 and |24 and the ,relay contacts 39.

The igniting means |28 is energized from the conductor |24 and-the conductor |23 through contactsl 4| in series with the ignition switch contacts 94 and the combustion responsive contacts |91 in series parallel relation with the ignition switch contacts 88. and the relay contacts 38. The ignition switch heater 14 is energized in parallel with the ignitingtmeans in series with th voltage dropping resistor |29. f i As a result of this action the lock switch motivating heater 59 is energizedcausing the active bimetal 51 to deect'towards the left, and the ignition switch heater 14 is energized and heats the active bimetal 88 causing it to build up effort in a direction away from the panel I8 and `in opposition to the magnetic effort due to the per- Normally combustion isalso established and the'thermal element 45-48 heats friction4 insulating member |08. After a short time the contactsllll'open the starting circuit for contact with 'the the relay but since a holding circuit has been established through relay holding contacts 38 the relay remains energized throughv a circuit extending from the conductor |23, through relay contacts 30, through the lock switch contacts 85 and the reset contact 81, through'the transformer primary winding 25, through the relay 28 to the conductor |24. The igniting means also remains energized througha circuit path extending from conductor |23 through relay contacts 38, through ignition switch contacts 88, through relay contacts 4|, through the igniting means |`28 to the conductor |24. The combustion responsive conf tacts |05 close at approximately the time-combustion responsive contacts |01 open. This energizes the lockout switch compensating heater 82 causing the compensator blade 58 to deflect to the left to follow the deflection of the active bimetal blade 51 and thus keep the circuit to the relay 28 closed at contacts 85. 'After some time, for example 90 seconds, the ignition switch active blade 88 reaches a high enough temperature to stress the ignition. switch assembly a suiiicient amount to cause the ignition switch 'armature 15 to spring away from the permanent magnet 81. The effort which causes the snap action of the armature 15 stresses the entire ignition switch.

assembly which consists of the adjusting screw 85,Y the adjusting lug 84, the compensating bimetal element 11, the U-shaped hinge bracket 88, the active bimetal blade 88 and the armature 15. The reactive opposing force ultimately appears between the adjusting screw 85 and the panel |8. (See Figs. 71, 8 and'9.) When the active blade 88 snaps away from the magnet 81, the spring latch |00 immediately assumes a position perpendicular' to the panel V|8 and the catch vice becomes inoperative.

Normal shtdown Assume that' -the control is functioningasstated above, and that the room thermostat |25 is satisiied and opens its contacts.- The open secondary of the transformer 25 immediately causes thecurrent in the relay circuit to drop to a very small value'. The relay releases its amature and the relay contacts' 38,38 and 4I open, deenergizing the fuel feeding means |28 and opening the holding circuit for the relay 28 at contacts 38. "The interlocking arm 33 together with its armature 32 swings toward the panel and encounters the slide release |0|A on the yspring latch |00 moving the catch |0| out' from under the ignition switch armature 15. 'I'his allows the armature`15 to return to its initial clbsed position under the attractive eiort of the permanent magnet 81, and causes the ignition'switch contacts 84 and 88 to close and partially complete the starting circuit for the .relay 28. (See Fig. 6.) It w ill be seen that both contacts 84 and 88 Vmust be closed before the starting circuit is complete. This insures that the ignition-means will 7 be energized before the fuel feeding motor 'can be energized.

The projection ||8 on the insulating' interlocking arm 33 of the relay 28 also encounters one portion of the combustion responsiveswitch contacts |08 causing them to open and deenerg'lze the motivat ing heater -822 As a further re'sult of the-relay action combustion is discontinued and the ther mal responsive element -48 cools and "causes |0| moves directly below the armature 15 in order that the armature 15 may not again return to its initial position. unless the electromagnetic relay 28 resets the ignition switch (see Fig. 8). action will be more fully explained hereinafter.

The S-shaped bracket |05 serves'to limit the motion of theignition switch armature 15 and therebyprevent it from snapping out'of the range of the permanent magnet 81. When the ignition switch armature 15 springs away fromthe magn'et ,81 the ignition contacts 94 and 98 open interrupting the circuit to the'igniting meansand the igniting switch motivating heater 14 and opening the starting circuit for the relay 28. The spring blade 85 assumes a p'osition` midway between the contacts 84 and 88. As time goes on the slip friction insulating member |08 eventually reaches the hot stop |I8 and the slip connection actuates causing the slip friction blade 48 to slide between the friction blades 55. Eventuallygthe lock switch active bimetal blade 51 and compensating bimetal blade 58 reach their ultimate heated positions and the ignition switch. active bimetal-blade 88 cools to the ambient temperature. As the bimetal blade 58 cools'it encounters the catch Ill on the spring latch |00 and can then deflect no farther toward the panel. (See Fig'. 8.) As additional cooling takes place', however, the U-shaped hinge vbracket 88 rotates under the deecting action of the bimetal 88 .-causing the compensating blade 11 to elevate and lift the adjusting screw 85 out of contact with the panel. The control device is now in the normal running position andthe various component parts ofi the structure will remain `as posifarther.

the immediate clockwise rotation of'the slip friction insulating member |08. vAfter the tempera- .ture of the thermal responsive element has dropped a predetermined amount, for example 80; the thermaI responsivecontacts |01. close to complete the line voltage s ide of the starting cir-.

cuit for the relay 28.` Upon further cooling of the u thermal element 45-48 the insulating member |08 engages the cold stop ||4 and can move no operate and the slip Vfriction blade 48 slides between friction blades 55.

It is to be understood that during this interval of time the lockA s witchmotivating heater 58 has been deener'gized in response to the thermostat |25 action, as well as the compensating heater 82.'

Vvand the two lock switch bimetal blades 51 and 58 are cooling to theambient temperature.

and 5 0is complete, the controlwill be in a normal startingposition and the ignition switch will be positioned as vshown in me Figs. 4, v5 and 6.

ltioned 'untilv the automatic control device |25 is satlsed, a combustion failure occurs, a power v ignition failure Assume that the control is in the nonnal start'- ing. position and that the thermostat contacts |25V close in response tothe temperature in the space being heated. The relay 28 will thenoperate in response to the transformer` 25 action as stated above. The fuel feeding means |28 and'lgnition ineans |28 will be energized as well as the motivating heater 58' for the active blade of the ignif tion switch 88V. Assume now that combustion is not established because o f failure in the igniting means'or for some other reason, so that the thery mal element 45-48 will not be heat'e'd'and c onsequently'the slip friction insulating member |00 will A.not 'cause any action of the combustion responsive contacts |08 and |01. Under these circumstances the`com'pensating heater 82 will failure occurs or some elementin the control de- Continued motion of the thermal ele- 4ment 45-48 then causes the slip connection to When thecooling of the lock switch bimetal blades 51 Normal starting.

`Aruption ofvpower occurs.

the relayA 2l not be energized. As time goes on the active blade 61 will deflect away from the compensating 'i blade 68 and the relative distance between the two will increase until the latch 64 trips and opens the circuit through the relay 26 at contacts 66. This tripping action is adjustable and may be set for ninety (9 0) seconds, for example, Aafter tion of the relay complete shut-down of the system, and another operating cycle cannot be initiated until the lock Vswitch is manually reset by use of the lever 66.

As may be seen from Fig. 1 or Fig. 10, moving the `lever 66 upward causes it to engage thelatch 64 and lift the latehto its normal operating position causing the closure of the contacts 65. So long as the lever 66 is in its raisedposition, the reset contacts 61 hold the relay circuit open. This prevents operating the system by holding the lockout switch `in the operating position by articial means.

During the 'interval of time, from the energization of the fuel .feeding means by the thermostat |25 to the deenergization ofthe system by the lock switch, the ignition switch functions kin exactly the same manner as. outlined under The ignition system timing and the lockout switch are entirely divorced under these circumstances. Q K

' Flame failure Assume `now that the system has progressed through a normal starting operation, has been operating for some time and that now for some reason there is a flame failure.V Under these circumstances the thermal element 45-46 cools and causes `the clockwise rotation of the slip friction insulating member When the temperature drops in excess of a certain-predetermined amount, for example 80, the contacts |06 open the circuit through the compensator heater 62.

right awayirom the active blade' 61, which is still being heated. After a short interval of time, the distance between the two blades becomes great enough to allow the release ofthe latch member and the contacts 66 open, causing-the deenersization of .the relay 26 and a complete shut-down of the system. Now, as in the case of the ignition failure' operation. the'system cannot be made operative untiithe lock switch latch 64 is manually Power failure during a normal running'periodA Assume that the system has progressed'through a normal starting operation, has been running satisfactorily for some time, and ashort inter- Under these conditions drops out, immediately opening the contacts 3l. 30. Il and |66, associated 'with it. 'Combustion also ceases immediately and the power is again established immediately after this interruption, thecontrol will'not theslip friction'insiilating anni will `not have sumcient time to move trom its hotposition toward its cold position'.

and the contacts |01 operated by it will remain open, so that there is `no starting circuit for the relay 26. However,

when the temperature `o! the thermalrelement 06-66 drops suflicientiyfan 80 for example, the

slipjfriction insulating member |06 will have rotacts |01 and a starting circuit for the relay will 26 by the lockswitch causes a4 -trol will stand by until the The compensator blade 66 startsto cool immediatelyand deilects toward the operate, since tated suillciently to cause the closure of conbe established. When the starting circuit is re- 75 established the relay 26 immediately pulls in and the system progresses as it would under a normal starting operation.

Powerjailure d urng a subnormal running period Assume that th system has partially progressed through a normal starting operation and that a short power failure occurs. Under these circumstances it is likely that the thermal elem ment e-46 will have reached asuiiiciently high temperature to have just operated the contacts |06 and |01, but that the ignition switch has not snapped open as yet, although it is on the verge of doing so. When the power failure is experienced,

la the relay 26 immediately releases its armature 21 and causes the interlocking armature 32 to revolve and come to rest in itsv normal standby position directly above the permanent magnet 81. In this position, the interlocking armature 32 2 shades the permanent magnet v81 to a marked degree and causes the magneticattraction on the ignition switch armature 15 to diminish a considerable amount. At the time or the power failure the ignition switch assembly exertsa substantial force in opposition to the magnetic effort, but .this force is insufficient to nullify the magnetic attraction of the unshaded permanent l magnet. Now when the magnet is shaded by the armature '32 the effort of the ignition switch assembly exceeds that of the shaded permanent magnet and the ignition switch snaps open. If

power is immediately returned, the system will n ot operate since the. starting circuit for the relay 26 is open at contacts 9| and 99. The conignition switch bimetal 66 cools a predetermined amount and the armature 15 deflects toward the permanent magnet until the magnetic eio'rt o! the shaded permanent magnet 81 is sufficiently strong to cause the ignition switch armature 15to snap back to the closed position. When this occurs, contacts 64 and 99 close and partially complete the starting circuit for the relay 26. However, the thermal responsive contacts 50 thermal responsive contacts |01 to close. When the starting circuit for the relay is completed the control will proceed with a normal starting operation as stated above. It is to be understood that under any circumstances the initiation of a burner operating period is prevented bythe warp switch contacts until the difference between the warp switch temperature and the ambient tem- I perature is below a predetermined amount.

A second form of the system is shown in Figs. i2 and 13. Here vthe combustion responsive conof tacts |01 have been removed from the starting thermal lelement ll--ll `proceeds to cool. It

circuit .in order to enable the control to start the burner independent oi' combustion conditions and toconsequently prevent delay between normal successive burner operations.V The voltage dropping resistor |20 of Fig. 10 has been divided into resistors Ill and |32. Normally open combustion responsive contacts III have been substituted for normally closed combustion responsive contacts .|01 with the contacts |33 arranged to shunt the resistor III shortlyafter combustion is established to increase the heat generated by heater Il and 'to consequently shorten the length of the ignitionperlod.

The circuit tion ofthe compensator heater |01 must also be closed. inv 45 addition before the .relay may pull in. lIn a normal installation by the time the` ignition bimetal- A operating with the relay starting the operation i warpswitch for controlling the ignition.

. with a ofthe burner, magneticrmeanasfor norconnected in parallel with the active heater 59 in series with the normally open combustion responsive contacts |08.

Under normal starting conditions this modiication will function identically as the rst form of the invention except that the ignition period will not be of a predetermined length but will be modified somewhat upon combustion conditions. The control action under normal shutdown, ignition and llame failure conditions will also be identical with that of the ilrst form of the invention, but the control action under power failure conditions may be somewhat diiferent depending upon circumstances-` In the case of the modification, in the event of a power failure during a normal a delay, in initiating a burner operating period upon the of a burner operation is in no way dependent upon combustion conditions and it is not necessary 'for the insulating member HI8 to return to the cold position in order to reestablish .a starting circuit for the relay 2B through combustion responsive contacts.

Upon a momentary power failure during a subrunning period, there is never ture and warp switch. said latch member arranged to vbe released by the operation of the relay amature so as to prevent the warp switch from moving to circuit closing position after havlng been operated, whereby a minimum ignition timing period is provided.

4. A burnercontrol system comprising means for feeding fuel to a burner, means for lgniting the fuel, magnetically biased thermal means for rendering said igniting means effective for a time period upon each successive normal operation of said fuel feeding means, a lockout moans for rendering said system inoperative in the event of ignition or combustion failure, and-means responsive to combustion for rendering the lockout switch inoperative during normal combustion and for shortening said ignitlng time period after combustion is established.v

lresumption of power since the initiation normal running period the modification of the invention will delay initiating a burner operation only so long as is required for the ignition switch bmetal 58 vto cool and close contacts 94 and 99. There can be no additional delay interposed because of combustion responsive conditions as in the case of the rst form of the invention.

While the features of the invention have been illustratedand described in only a few of their practical applications, it will be understood that other applications thereof may be apparent to those skilled in the art and it is therefore desired that the invention be not limited to the particu-l a lar disclosure made herein, but only by the scope of the appended claims.

What is claimed is; 1. In an intermittent ignition type oil burner circuit, the combination of a relay for controlling the burner operation timer for disconnecting the burner ignition means, magnetic means for 4biasing the warp switch in circuitclosing circuit opening position,

for preventing the warp switch from moving to` l peration.

of a relay amature for cuit, they` combination y offthe burner together timing mally biasing the relay amature in circuit open-7 ing. position and the in its normal posi'- for opening poinuonand with the relay annatogether with a warp switch position and the relay in and a latch member co-l permitting the said together with a warp dluration of the'lgni-f closing position, and

closed positions, a latch.

warp switch lncircuit closing and aspring latch vmember having two projections thereon,` one of said projections engageable by the yrelay amature tion to hold the other projection out of engage e -mentof the warp switch, and

Y other projection .to engage the warpswitch after- .the relayrarmaturehasoperated'.. I A l -.3. In intermittent ignition oil .burner circuit,`

-the combination of arelay operation `ofthe burner v switch timer for timing the magnet Kupon .said

5. A burner control system comprising, means for feeding fuel to a burner, electrical means for controlling said fuel feeding means, means for igniting the fuel. magnetically biased thermal means for rendering said igniting means effective for a time period upon each successive normal operation of said means for rendering said system inoperative in theevent of ignition orA combustion failure and magnetic. interlocking means cooperating with said fuel controlling means and said ignition controlling means for insuring at least a minimum predetermined ignition period after energization of said fuel controlling means.

6. A burner control system comprising means for feeding fuel to a burner, means for controlling said fuel feeding means, means forvigniting the fuel, magnetically biased thermal means for rendering said igniting means effective for a time yperiod upon each successive no/rmal operation of said fuel feeding means, a lockout means for rendering said system inoperative in the 4event of ignition or combustion failure, means responsive to combustion for rendering said lockout switch inloperative and for shortening said'ignition time period upon the establishment of combustion, and .magnetic interlocking means cooperating with lsaid fuel controlling means and said ignition con- -trollingmeans .for insuring at leasta minimum ypredetermined.ignition period afterlenergization' P of said fuel controlling means. .d

circuit closing Position- ,i means, means, an electromagnetic relay g 7. control ,system comprising, fuel feeding for controlling Saidfuel means and igniting means having open and closed positions, a 'thermal operated switch for additionally controlling '.the'igniting means l cooperating A with said electro-magnetic ,relay vand with said thermal switchv for holding the thermal switch in said open position once it Ihas reached that position solong Vils-fthe electromagnetic relay is in the4 closed punition,l said latch said-.electromagnetic relay in the open position andsaid thermal operated switchinvthe closed and said electromagnetic relay arranged the attractive eil'ortfofsaidpermanent thermal switch. v 8. A'burn'ercontrol system comprising. means v l for feeding fuel toa burner,.means for. igniting f5 `the fuel, means forsccntrolling thelength of time fuel feeding means, a lockout having open and the igniting means is energized, said means including a pairtof bimetal velements arranged to f elements, a heater for one of said elements for motivating the same, a plurality of contacts operated by said bimetal elements,- a permanent magnet for biasing said bimetal elements in a direction so as to close said contacts, an electromagnetically operated armature cooperating with said permanentmagnet to modify the `biasing effort of said permanentmagnet upon said bimetal elements to insure that the igniting means is energized for at least a predetermined minimum length of time.

9. A burner control system comprising, means for feeding fuel to a burner, means for igniting the fuel under normal and abnormal conditions, first switching means for controlling the energizaticn and deenergization of said fuel feeding means, second'switching means having first and second positions for controlling the energization and deenergization of said igniting means, said. second switching means arranged to normally move from its first position to its second position after the expiration of a predetermined time i`nterval which is initiated at the time said fuel feeding means is energized, and said rst switching means arranged to mechanically cooperate with said second switching means under normal conditions to cause said second switching mea-ns to return to. its first position immediately upon the deenergiza'tion of thel fuel feeding means but under abnormal conditions to magnetically cooperate to cause said second switching means to return to its first position after a time delay following deenergization of the fuel feeding means.

10. A burner control system comprising, a motor for feeding fuel to a burner, an electric means for igniting the fuel, a circuit for the motor, a relay for controlling the motor circuit, a circuit for said relay. a circuit for said igniting means, a thermally operated switch having first and second 4positions for controlling the igniting circuit-and the relay circuit, two pair of contacts on said thermal switch, a safety switch for additionally controlling the relay, a pairof mutually coupled reactance coils, a'source i' power, said relay, one of said reactancecoils, said safety switch and said thermal switch contacts all connected inv series arrangement across said source of power.` a pair of contacts on said relay connected in parallel with said thermal switch contacts, a second pair of relay oontacts, one Vof said pairs of said thermal switch'contacts and said second pair of relay contacts connected inseries with said igniting means acrossl theA soirce o! power, a heater for motivating said thermal switch, a voltage dropping resistor, said resistor and said heater connected in series circuit arrangementl in parallel with said igniting means, a combustion responsive switch, a pair of conso l for feeding fuel .to a

for feeding fuel to a burner, means for ignitingthe fuel, an electromagnetic relay having open `and closed positions for controlling the. energizeerated snap action switch in the open position onceit has reached this position so long as the electromagnetic relay is in the closed position but permitting said thermally operated snap action switch to return t'o its closed position solong as the electromagnetic relay is in the open position, cooperating means between said electromagnetic relay and said thermally operated snap action 'switch for causing said thermally operated snap action switch to open prematurely in the event said electromagnetic relay returns to the open position before the normal ignition period has expired but after a second predetermined period has expired, said second predeterminedV period being equal to the first normal ignition period minus a predetermined minimum ignition period, and means for rendering said system inoperative so longr as both said thermally operated snap action switch and said electromagnetic relay are in the open position.

l2 A burner control system comprising, means for feeding fuel to a burner, means for igniting the fuel, an.' electromagnetic relay for controlling the fuel feeding and the ignitionmeans, a therriod magnetic interlocking means cooperating with said relay and said thermal snap switch for preventing the initiation of an operating period in the event that said thermal snap switch would be unable to provide at vleast a minimum predetermined ignition period.

13. A burner control system comprising, means burner, means for igniting the fuel, an electromagnetic relay having open and closed positions for tion and deenergization oi' said fuel feeding means,` a thermally operated snap action switch hailing open and closed positions for controlling y `themnergization land .deenergization of the 1gtactson saidswitch connected in parallel with said voltage' dropping resistor, a motivating heat-` er 'for said safety switch, an automatic operating device, said loperating device and said safety switch heater connected in series circuit arrangementacross said second reactance coil, a second motivating heater for the safety switch,a second pair of contacts on the combustion responsive switch. and said second safety switch heater and said second pair of contacts connected in series circuit arrangement in parallel with the first motivating heater. Y v

ll. A burner control system comprising, means niting means,

said thermally operated snap action switch operating to normally give a predetermined ignitionV thermally operated snap -action switch in the open position once-it has reached this position so'long as the electromagnetic relay is in the closed position but permitting said thermally operated snap action switch to return to its ,closed position so long as the open position, cooperating vmeans between said electromagnetic relay and said thermally operated snap action switch `for causing said thermally-operatedA snap action `'switch to open prematurely in the eventV said electromagnetic relay returnsto thel open position shortly before the normal ignitionV period has expired, and means responsive to combust on for interposing controlling the energizaperiod. means cooperating with said electromagnetic relay for holding said the electromagnetic relay is in' delay between successive burner energizations.

14. A burner control system comprising, means for feeding-fuellto a burner, means for igniting the fuel, a line voltage circuit, an electromagnetic relay in the line voltage 4circuit for controlling the fuel feeding and the ignition means, a thermally operated snap action switch having open and closed positions for rendering said igniting on said relay for increasing thel pull-in voltage4 of said relay, for releasing said retaining latch, and for shunting said'permanent magnet to cause the release and opening. of-said thermal switch and thereby prevent the initiation ,of an oper-V ating period. -in the event that said Ithermal snap switch is closed and *unable to provide at least a minimmn. predetermined ignition period, a thermally operated lock-out switch for rendering said system inoperative in the event of ignition or combustion failure, a low voltage operating device, means for operating said relay in the line voltage circuit by said low voltage device, means responsive to dierences in combustionconditions for controlling said lock-out switch and for moditying the length of said ignition time period.

l5. A burner controlsystem comprising, means for feeding fuel to a burner, means for4 igniting the fuel, a line voltage circuit, an electromagnetic l .relay in the line voltage circuit for controlling the fel feeding and the ignition means, a thermaily operated snap action switchhaving open and-closed positions for rendering said igniting means eifective for a timed ignition'perlod upon each successive normal operation of said fuel feeding means and for initiating each successive burner operation, a. bimetalactuator for actuating said snap Vaction switch, c permanent magnet fory biasing the -switch in 'a closed direction,

and a heater energized during'theignition period fonly for motivating the actuator in a direction to open the switch.l a retaining latch for holding the'switch open' once -it has reachedthe open position, means for supporting the actuatorkand compensatingthe actuator'ior :changes in ambient temperature whereby theeort exerted byl in combustion conditions for controlling said lock-out switch and for modifying the length of said ignition time period- Y 16. A burner control system comprising, avfuel feeding motor, an igniter, a line voltage circuit for s'aid motor and igniter, a step-down transformer having primary and secondary coils, a relay connected in series with said primary coil for controlling 'the circuit to said motor and igniter, condition responsive means in series with said secondary coil for controlling the energization and deenergization of said relay, a normally closed warp switch energized simultaneously with the motor and igniter for deenergizing both the igniter and itself upon movement away from the closed position after a time period, a magnet arrangedl to bias the relay toward its deenergized position and to bias the warp switch toward its closed position, a latch arranged to hold the warp switch away from the vclosed position, said relay arrangedV upon deenergization to operate the latch and release the warp switch, a time delay'manually reset lock-out switch for rendering the system inoperative including an actuator energized by the condition responsive means for opening the lock-out switch, and combustion responsive means for preventing the opening of the lock-out switch during the existence oi combustion.

17. A burner control system comprising, a fuel feeding motor, an igniter, a line -voltage circuit for said motor and igniter, a step-down transformer having primary and secondary coilsl a relay connected in series with Said `primari? GOil for controlling the circuit to said motor and igniter, condition responsive means in series with said secondary coil for controlling the energization and deenergization of said relay, a normally closed warp switch energized simultaneously with the motor and igniter for deenergizing both the igniter and itself upon movement away from the closed position after a timed period, almagnet arranged to bias the relay toward its deenergized position and to bias'the warp switch toward its closed position, a latch arranged to hold the warp switch away from the closed position, said relay arranged upon deenergization to tne'switch on the retaining latch is substantially that due to the'bianng enprt ofthe permanent magnet alone when said switch is in the open position, interlocking means on said relay for in- 'f creasing' the pull-inlvoltage of saidl relay. for releasing said retaining latch, and for shunting said permanentmagnetto causev the release and opening of said thermal switch and thereby prevent'the initiation of an operating period in the f event said thermal snap switch is closed and unable to provide -at least a minimum predetermined ignition perlod, a thermally operated lockout` switch for Arendering said system inoperativein? the event of ignition orcombustion failure, a Ilowivoltage operating device; means for operating in the line voltage circuit lby said low :voltage device, means responsive to diiierences 'for said motor Iand operate the latch and release the warp switch, a time delay manually reset lock-out switch for -deenergizing the system including a first actuator energized by the condition responsive means concurrently withthe relay for opening the lock-out switch, and a second actuatorgenergized by combustion responsive means for.` preventing the opening of the lockout switch during the existence'of combustion. i

- 18. A burner control system comprising, a fuel feeding motor, an igniter, a line voltage circuit Y lsniter, a relay for controlling the circuit to Vsaid motor and igniter. condition responsive means for controlling the energization and deenergization of. said relay, a warp switch y having normally closed contacts in series with said relay lfor initiating the enersization of the' relay and for additionally controlling the igniter, a heater energized coincidentally with the igniter for heating and ,motivating the warp switch to open the normally closed contacts'and render the igniter and the heaterl ineffective 'after' a time delay, a magnet arranged to bias .the relay toward its deenergized position to prevent the relay from pulling in*v at a low voltage and to bias the warp switch in a direction tc close the normally closed -contacts'and render the warp switch ysilp acting, a latch an integral catch and a slide arranged to provide cooperative action between the relay and the warp switch, said catch disposed to restrain the warp switch after each ignition period expires to prevent the normally closed contacts from closing after the heater is deenergized and the warp switch cools,

l interlocking means on .the relay for engaging said slide and operating said catch to relase the warp vswitch and permit the normally closed contacts to close at the end of each burner operating period, said interlocking means `being additionally arranged to diminish the biasing effort of the magnet rupon the warp switch and cause the warp switch to open the normally closed contacts in the event the warp switch is heated above a predetermined amount to prevent the initiation of a burner operating period until the warp switch is cooled, a time delay manually reset lock-out switch for rendering the system inoperative including an\ actuator energized by the condition l responsive means for opening the lock-outswitch, and combustion responsive means for preventing the opening of the lock-out switch during the existence of combustion. l

19. A burner control system comprising, a fuel feeding motor, an igniter, a line voltage circuit for -said motorV and igniter, a relay for controlling the circuit to said motor and igniter, condition responsive means for controlling the energization and deenergization of said relay, a warp switch having a hot position and iirst and second cold positions, a pair of contacts closed in the first cold position and open in the second cold position for initiating operation of the fuel feeding Y motor and controlling the igniter, a heater energized coincidentally with the igniter for heating and motivating the warp switch away from the cold position to the hot position to open the contacts and render the igniter and the heater ineffective after a time delay, a latch cooperating with said warp switch and said relay for restrainingthe warp switch at the second cold position when said warpswitch cools from the hot position so long as the relay isclosed and to permit the warp switch to move from the second cold position to the rst coldposition when the relay opensfmagnetic interlocking means on the relay cooperating with the warp switch to prevent the initiation of a burner operating period by the warp switch contacts until the 4difference beween the warp switch temperature and the ambient temperature is below a predetermined amount, a time delay manually reset lock-out switch for rendering the system inoperative including an actuator energized by the condition responsive means for opening the lock-out switch, and combustion responsive means for preventing the opening of the lock-out switch during the existence of combustion. 1

20. An automatic oil burner system comprising a burner having a burner motor, an operating circuit for said burner motor and a relay switch controlling said circuit to start and stop said burner, a control circuit for said relay switch including l a room thermostat, electric ignition means energized by closure of said relay switch, an ignition cut-off switch adapted to b e opened to de-energize said ignition means, a thermal timer for controlling the opening of said cut-off -switch comprising a pivoted carrier having a compensating bimetal element and an active bimetal element similarly mounted and positioned thereon* to assume related positions in response to variations in ambient temperature, an abutmentagainst which said compensating element 75 may bear, timer positioning means operable upon said pivoted carrier with a yielding force to maintain said compensating element against said abutment, a heater for said active element, said active element actingV normally when cold to maintain said ignition cut-off switch closed and operable when moved to its hot position by heating to ,cause opening of said ignition cut-olf switch, an energizing circuit for said heater, a switch operable under the control of said timer to de-energize said heater when said ignition eut-off switch is opened, latch means operable to latch said active brnetal element of said timer in its hot position, said timer positioning means acting with a yielding force on said timer urging said control circuit and saidcombustion re.

sponsive means, and means operable by said reto' release said active birnetalelement of the timer for return to its cold position.

21.A control system for fluid fuel burners comprising in combination, an electrical Vfuel feeding device, an ignition device for the fuel, a circuit for said electrical fuel feeding device, a relay which when energized closes said circuit to said fuel feeding device, first switch means responsive to the demand for heat controlling vlay when released to operate said latch means said relay,'a circuit for said ignition device also l closed upon energization of said relay,v and including a 4further switch means so arrangedthat the ow of current through said ignition device is independent of said first switch means except as said first switch means controls the operation of said re1ay,means formoving said second switch means to open position following the successful establishment of combustion, and means preventing the original energization of said relay by said first switch means unless said second switch means is in condition to pass current.

22. 'A control system for duid fuel burners comprising in combinatioma1 source of power, a transformer having primary and secondary windings, switch means, means connecting said primary winding across said source of power including said switch means, an electrical fuel feeding device, an ignition device for the fuel, a relay, a condition responsive device in circuit Withsaid secondary winding for operatively energizing said relay, said relay upon energization establishing a circuit for said primary windingindependent of said switch means, a circuit for said fuel feeding device and a circuit for said ignition device, the circuitfor said ignition device including said switch means, and means for moving said switch lrelay, -a condition responsive device in circuit with said secondary winding for operatively energizing `said relay, saidA relay upon energization establishing acircuit for said 'primary winding independent of said switch means, a circuit for said fuel feeding device and a circuit for said ignition device the vice including said tomatcally moving ,said switch means to open position to terminate ignition yafter said fuel relay, a condition responsive switch `in circuit with said secondary winding for operatively energizing said relay, said. relay upon energlzation establishinga circuitdor said primary winding independent of said first named switch means. a circuit for said fuel feeding device and a circuit for said ignition device, both circuits being.

normally closed upon energization of said relay, the circuit for said ignition device including said rst named switch means so arranged that the flow of current through said' ignition device is independent of said condition responsive switch except as said condition responsive switch con.-

circuit for said ignition deswitch means. means for aua Source f POWER',v

'fcrbiasing said thermal responsive switchingl electrical fuel feeding device, anignition device for the fuel, a

. ing and stopping the trols the operation of said relay, means for automatically moving said first named switch means to open position to terminate ignition after said -fuel feeding device has been energized 'and for automatically reclosing said switch means as an incident to the termination of combustion.

25. In a control system for an electrical device, the combination of, a relay having a coil, an armature, thereby, said switching mechanism being moved to closed position by said armature when the coil is energized and being moved to open position by said armature when the coil is deenergized, a

source of line voltage alternating current power,

electrical connections including said switching mechanism and connecting said electrical device to said source of power, a choke having a primary and secondary, electrical connections continuously connecting ondary for selectively causing energization or substantial deenergization of said relay coil,v and means including a permanent magnet for biasing said amature away from the relay coil, said magnet increasing the current flow through the relay coil necessary' to cause movement of said amature to its energized position and also tending to stabilize the position.

and switching mechanism actuated the ow ofl current through said sec-A s to electrical device in series for i armature in its deenergized means toward one of its positions, and means controlled with said fuel feeding means for con-- trolling said magnetic biasing means.

27. In an intermittent ignition type burner control system for controlling a burner having fuel feeding means and igniter means, the combination of, means for starting and stopping the fuel feeding means, thermal responsive switching means arranged to control said igniter means and movable after starting ofthe fuel feeding means froma first positionrendering the igniter means operative to a second position rendering the igniter, means inoperative, means lfor biasing said thermal responsiver` switching mechanism toward'its first position for delaying movement thereof `toward its second position, and means actuated upon stopping of the fuel feeding means for reducing the effect of said biasing means.

28. In a control system for a burner, the combination of, means including a device responsive to the demand for heat from the burner for startsame, means including thermal responsive switching means arranged to cooperate with said device in controlling the burner, said switching means having a first position which conditions the burner for starting and a second position which prwents starting of said burner, means for causing said switching means tomove from its first position to its second posi- `tion a period of time after starting of the burner.

and to return to its rst position upon stopping of the burner, biasing means for biasing said switching means toward its first position, and means controlled with the burner. for reducing the eifect of said biasing means upon stopping of a second position which prevents starting of said burner, means for causing said switching means move from its first position to its second position a period of time after starting of the burner and to return to its first position upon stopping of theburner. magnetic biasing means for biasing said thermal responsive switching means toward one of its positions, and means controlled with the burner for varying the effect of said magnetic biasing means.

30.4 In an intermittent ignition type burner control system for controlling a burner having fuel feeding means and igniter means, thecombinatio of, means including a device responsive to the demand for heat from the burner for starting and stoppingthe including thermal responsive switching means arranged to control the igniter means and the fuel feeding means and ditioned to start and the igniter means rendered operative to a second position in which starting of the fuel feeding means is prevented and the igniter meansis rendered inoperative; means for `causing said thermal responsive switching meansswitching means arranged to fuel feeding means, means.

movable from a first position in which the fuel feeding means is conber, meansl hinge W means toward its iirst posion and means actu' ated upon stopping of the fuel feeding means for reducing the effect of said biasingl means.

3l. A control system for a burner having fuel feeding means and an igniter, the combination of, a relay adapted to place the fuel feeding t means into and out of operation, igniter/ control means for' controlling the igniter and eective to render the same operative when, the fuel feeding means is placed into operation and to render the igniter inoperative a period of timethereafter, said igniter control means comprising a pair of bimetal elements arranged to compensate each other for changes in ambient temperature, a hinged support for both of said bimetal elements, each bimetal element having one end' fixed to the hinged support and` the other end free to move with respect to the hingedv support,A

adjustable stop means associated with the free end of one of said bimetal elements, biasing means for biasing said free end' against said stop` means, igniter Icontrolling switching mechanism actuated by the free end of the other bimetal element, a heater for one of said elements, means for controlling said heater and operative to cause said last mentioned element to change in temperature in a ilrst direction when 'the fuel feeding means is placed into operation to cause actuaf tion of said igniter controlling switching mechanism for rendering the igniter inoperative, means controlling said heater for causing itsassociated bimetal element to change in temperature -in the opposite direction when the igniter is rendered l inoperative,l latch means for preventing return movement of said last mentioned element. and means actuated with said relay for releasing said latchy means when the fuel feeding means is placed out of operation. y L

32. `A burner control system for a burner having fuel feeding means and an igniter, theicombination of, means for placing the fuel feeding means into and out of operation, ignitcr control meansfor controlling the igniter and effective to render the same operative when the fuel feeding means is placed into operation and to render the igniter inoperative a period of time thereafter, said igniter control means comprising. a pair of bimetal elements arranged to compensate each other for changes in ambient temxulraturc.V a hinged support for both of saidbimetal elements, each bimetal element having one end^ fixed to the hinged support and the other end free to move with respect to thehinged suDPOrt. ad-

, justable stop means associated with the free end' of one ofsaid bimetal elements. biasing means for biasing said free end against said stop means, igniter controlling switching mechanism, actuated by the `free end of the other bimetal element, a heater for one o f said elements. and means for controlling said 'heater and operative to cause 'saidlast mentioned element'to change in temperature when the melfeeging means isplaced intooperatlontocameactuationofsaidigniter the igniter inoperative.'`

. y 1 1 attaching said supporting member to said base member, a pair of bimetal elements mounted side" by side on said supporting member, each bimetal element having one end attached to' said supporting member and the other end free to move with respect to the supporting member. adjust-V able stop means associated with the free end of one of said bimetal elements and with said base member. biasing means for biasing said free end against said stopmeans, and switching mechanism supported on said base member and vcon-- trolled vby the free end of the other bimetal element, said switching mechanism controlling said burner. f

34. In a control system for a burner,` the combination of, means including a device responsive yto the demand for heat from the burner for starting and stopping the same, means including l a device responsive tothe demand for heat fromk switching means arranged to cooperate with said rdevice in controlling the burner, said switching means having a first position which conditions the burner for starting and a second position which prevents starting of said burnenmeans for causing said switching means to move from its iirst position to its second position upon starting ofthe burner and to return to its rst position upon stopping of the burner, biasing means for biasing said switching means toward its first position. and means controlled with the burner for varying the effect of said biasing means.

v 35. In a control system for a burner, the combination of, a twov position relay, means including the burner for controlling the relay to start and stop the burner, means including switching f means arranged to cooperate'with said device in controlling the relay, said switching means having a nrst position which conditions the relay for movement to one of its positions and a second position which prevents movement of the relay to said one position,- a first holdingmeans tending to hold the switching means in its first position, a second holding means tending to hold the switchingmeans in its second position, and means controlled by'l the relay for controlling both of said holding means.

86. In a control system for an electrical device,- the combination of. a relay havingaa coil. an armature, and switching mechanism actuated thereby, said switching mechanismbeing moved to closed position by said armature when the coil is energized and being moved to opn position by ,said armature when the coil is deenergiscd, a

sourceof electric power, electrical connections including said switching mechanism and elecf.l

trical device in series for connecting said electrim devieeto said source or power; electricas connections including a control switch for selectively energizing the relay coil from said source of power or deenergising said relay coil,

means including a permanent magnet for 4the armature away from said relay coil. saidmagn t ,increasingthecurrentilowthroughthereiay controlling` switching mechanism for rendering 83.Inacontrolsystelilforaburner.thecoml bination of,abasemember.a

necessary to cause movement ofthe armature to itsposition -wherein the switching mechanism connects the electrical device to the`so`urce of power. l l

IEWISLQUNNINGHAR, 

